Steering system



Jul le 27, 1950 B. o. STROTHER STEERING SYSTEM 2 sheets sheet 1 Filed July 31, 1947 MMA N INVENTOR. Bid/7 4 4 0. ff/v June 27, 1950 B. O. STROTHER STEERING SYSTEM 2 Sheets-Sheet 2 Filed July 31, 1947 steerable through an arc of 180.

Patented June 27, 1950 UNITED STATES PATENT OFFICE Claims.

This invention relates to hydraulic power drive systems. Although the invention is particularly applicable to systems for the operation of steerable elements, such as the wheels and rudders of land, sea and aircraft, and my preferred embodiment as herein disclosed comprises a system for steering the wheels of a motor vehicle, it will be recognized that the principles of the invention may readily be applied to other uses. An object of the invention is accordingly to provide an improved system adapted to impart to one or more movable elements, and to control the direction and extent of, angular, lateral or swinging movements which are accurately and quickly regulable under the direction of a single, manually operable controlling agency which may take the form of a steering wheel or the like.

It will be appreciated from the foregoing that in the following description, references to parts of a motor vehicle, and to other known elements with which my invention is adapted to coact, are intended in an explanatory sense and by way of example rather than as restrictive.

Another important object of the invention is to provide an improved system of the character indicated which is very flexible in character and which permits an operator or driver to control a plurality of steerable wheels or the like in such manner that steering movements may selectively be applied to some wheels but not others, as the operator may desire; or alternatively, different wheels may be made to swing either in the same direction or in different directions, again at the election ofthe operator.

By way of illustration, my improved system is herein disclosed in connection with a type of automobile so designed that all four wheels are This is made possible by the provision of an individual propelling motor (not shown) carried by each wheel of the vehicle, and by the provision of an independently sprung suspending structure for each wheel. The details of the automobile construction including the wheel suspension and the motor means above mentioned, form no part of my present invention and are known in the art. They are accordingly not illustrated herein.

I take advantage of the extreme steering movement of the wheels made possible by the aforementioned motorcar construction by providing steerable mountings for all four of the wheels, and incorporate in my preferred embodiment:

(a) Means for steering the front wheels only, while the rear wheels remain parallel to the center line of the vehicle (for ordinary-steering 2 while the vehicle is being driven under ordinary conditions) (b) Means for simultaneously steering the front wheels in one angular direction and the rear wheels in the opposite angular direction (to permit turning of the vehicle in a very short length), and

(0) Means for simultaneously turning the front and rear wheels in the same angular direction (so that the vehicle may be moved sideways or perpendicularly to its longitudinal center-line to facilitate parking and to permit lateral movement of the vehicle whenever desired, as when maneuvering in close quarters).

The primary objects of the invention may be summarized as comprising the provision of means for attaining the above-indicated ends and constituting a structure of compact, simple, inexpensive, rugged, and reliable character. I

Still another object is to provide a steering system of the indicated character permitting steering movements of the wheels in the conventional manner by means of a steering wheel, and incorporating a manual selector operable in a very simple manner, as by means of a single handle, whereby the action of the system may be varied to permit the imparting of different steering movements to the steerable wheels in response to turning of the same steering wheel. Thus, the same handwheel may effectuate steering movements of the front and rear wheels of the vehicle either independently or simultaneously in the manner above indicated.

Another object is to provide in a system of the indicated character novel interlock-ing means preventing changing of the steering relationship between the wheels except when the wheels are in predetermined positions (preferably parallel to the longitudinal center. line of the vehicle).

Still another object is to provide improved signal means adapted to inform the driver as to the condition of the steering system when it is so adjusted as to impart steering movements to the wheels in other than a conventional manner.

Another object of the invention is to provide such a steering system having a self-energizing or servo action and accordingly requiring very little manual effort on the part of the driver.

Other objects and advantages will be apparent upon consideration of the present disclosure in its entirety.

In the drawings:

Fig. 1 is a diagrammatic plan view of a vehicular steering system incorporating the principles of the present invention;

Fig. 2 is an exploded view of the selector valve, showing the valve plug in elevation and the valve casing in horizontal diametric section and substantially as indicated by the line and arrows 2-2 of Fig. 1;

Fig. 3 is an exploded view similar to Fig. 2 but showing the valve plug and casing only and taken at right angles to Fig. 2 and substantially as indicated by the line and arrows 33 of Fig. 1; Figs. 4 and 5 are fragmentary sectional views of the selector valve in difierent operative positions;

Fig. 6 is a fragmentary diametric sectional view of the valve latching means;

Fig. 7 is a rear elevational view of a part of the latching means, partly broken away; and

Fig. 8 is a partly diagrammatic elevational view of a part of the indicating system, on a larger scale.

Referring now to the drawings, and particularly'to Fig. 1, reference character It designates the chassis frame of a vehicle to which my improved steering system is illustratively depicted as applied. The frame It is fragmentarily indij thereon to swing 90 in either direction from the normal position corresponding to straight-ahead positioning of the wheel.

An individual hydraulic motor mechanism is provided for imparting steering movements to each wheel. Since'all of these steering motor mechanisms may be alike, description of one willsuflice. Each such steering motor mechanism consists of a single radial vane as [5R lying in a vertical plane and rigidly secured to and swingable with the stub axle l2 about the axis of the kingpin. The vane fits accurately within the semicylindricalhousing as 1BR. Steering is effected byselectively applying fluid pressure to the interiors of the steering motor housings of the several wheels upon one side or the other of the respective vanes of such motors, to swing the wheels as desired.

A suitable supply of oil or other substantially incompressible fluid is maintained in a reservoir from which it is pumped as by the gear pump schematically indicated at 22. The pump is preferably constantly driven by the engine of the vehicle and draws fluid from the reservoir through conduit 2|, delivering the fluid by way of conduits 23 and 24 to a steering valve, the casing of which is generally designated 25. The valve member 21 within the casing 25 is of the piston type, having a central spool portion 28 and left-end and right-end spool portions 3| and 32 ,respectively connected to the central spool 23 by the reduced stem portions 33-34. The valve piston assembly thus constituted is yieldably centered in the casing 25 by means of springs 36-31, one such spring being arranged at each end of the piston assembly, as shown. The fluid entering the central portion of the valve casing through an opening to which the conduit 24 is connected passes into a groove 4!) formed'in thead- 4 jacent face of the spool 28. When the valve assembly is centered, as shown in Fig. 1, the fluid may escape from groove 40 through a diametrically formed bore 4| extending through the spool 28 and connecting the groove 40 therein to the opposite face of the spool, at which opposite face the bore 3! registers with an escape port 42. When the piston assembly is centered, the fluid may return from port 32 to the reservoir 26 by way of conduits 54 and t5.

Groove Ml is long enough to bridge the space, and provide communication, between the central port 35 and either one of the two spaced ports iil 52. Both of the last-mentioned ports 5! and 52 are blanked ofi by the end portions of the spool 23 when the piston assembly is centered. The valve is also constructed so that when in the centered position all passages leading into and from the valve are isolated from one another excepting the inlet and return ports 35-42. When the valve is moved to connect ports 355l, it also connects conduits E52.93 and 1lll4 via the reduced portions 3 8 and 33 respectively. Similarly, when the valve is moved to the right to connect ports 3552, it establishes connection between conduits 'l893 and between conduits The ports 5| and 52 are connected to the opposite sides of a steering pump assembly generally designated 56 and which is preferably of a suitable, reversible, positive displacement type, such as a gear pump. One ofthe gears as 53 may be positively driven by the shaft 55 which is connected to and adapted to be turned by the steering wheel (not shown). Connection between port El and one side of the pump is effected by a conduit ti, while port 52 is connected to the other side of the pump by a corresponding conduit 62. Conduit 6|, is also connected to the left end of the valvecasing 25 by a branch conduit 63, and conduit 62 is similarly connected to the right end of the valve casing b a branch conduit 34. It will, therefore, be' seen that whenever a pressure difference exists between the conduits 6i and 62, the valve is moved away from the conduit containing the higher pressure,

, If the steering wheel is turned in a direction to increase the pressure in conduits 62, 64, as by turning the steering wheel to the right or clockwise, the steering'valve 21 will be moved to the left, as the parts are viewed in the drawing. The escape port 4| is'thereby closed and communication is established betweenports 35, 5| so that pressure fluid from the pump 22 now passes through the conduit GI to the'left side of the steering pump 59. Such fluid assists in the turning'of the steering wheel, and the pressure from the output side of the steering pump 50 is delivered through conduit 62 and valve chamber 34 to a conduit 33 leading to one of the ports as of a selector valve 51. The selector valve will be described in greater detail hereinafter, and serves the function of enabling the pressure fluid to be delivered to the individual steering motors in such fashion as to provide any of three different steering functions at the will of the operator.

With the selector valve in the position in which it is shown in Fig. l, which is the normal driving position in which only the angular positions of the front wheels are influenced by movement of the steering wheel, the fluid passes from port Q5 through the valve passage 'iS and by way of a conduit 99 and branch conduit it! to the front wheel steering motor casings [6B, ISL. It will 1 be seen that the conduits 99 and it! are so cons liver o 'the ee e moto nes; 5R ;;:l;5 -s sr e r tgw he. e v t ou c dui 02 1 3., I and bypiwayof valve chamber 33 and branch con u t a rnline .1 a n to th I Q' Q F-I .I 1 .jr; .1; --l;f movement of the steerin wheel is arrested to .hol dthe frontIwheelsat-a; desired angular p0,.- sition, the pressure in-condu-its B2, '64 drops and the springs 36, 31- return the steering valveto centered position, The gfluiddines '93,; I04.- to the steering motors are;thus;, isolated as-shown-in Fig.1.; trapping'the fluid in such. motors: and thereby lockingthevanes andthe wheels in the desired-. positions Fulfill]; the, steering- Wheel is eea m 1: :r 1 '1 Iii-the steering wheel is now turned to the left, asimilar operation to -thatdescribed for righthandturning will occur in the reverse direction. Pressurebuilds .upin fluid conduits 6 I 63 moving the steeringvalve piston. 21 1 to the right and again closing, the escape, portmortions AI, 42. Port 35 is thereby placed in communication with conduit 62by way of valve chamber- 40 and the fluid thereby; delivered to pump 50 provides a servoactionassisting in the turning of --the steer-'- in wheel to the left. Afterpassina through the steering pump 50, thel-fiuid isdelive-red by way of conduit-61 and valve chamber-33'toconduits I04; I 03,402, and thus to the front wheelsteering' motors ISR, IGL, entering these upon the op-. posite; sides of the vanes I53, I514, and so turning both front wheels to the left as will be ap parent; The fluid returned from the front steere ing motors during their leftward steeringmovement passes through conduit portions IOI, 99 and through the selector valve passage 13 and conduit 93 to the teer ng Valve body. The fluid then passes through the valve passage 34 to the branch return conduit 18. {from which it is.-returned to the reservoir by way of conduit 45 .as

before...-.

Itwill be observed that at all times when the power pump- 22 .is in operation, fluid under pressure is delivered by way.of conduit 23 to a port 89! of the selector valveassembly61, which has a rotatable tapered plug-type valve element 68. With the valve element 68 in the. middle or drive position inzwhich it is sho'wnin full lines in Fig. 1 (in which position only the front wheels are steerable), the, pressure fluid is conducted from port 89' through .a-valve passage 19 to a conduit 90 which enters one end of a locking cylinder I35. A piston I30 within the locking cylinder is thereby urged outwardly. A stem- I31 attached to the piston projects'from the cylinder and is at such time engaged in a notch I40 in the hub portion I4I. An arm I26 fast at its inner extremity to the hub I4'I is pivotally connected at its outer end to a tie rod I28 which connects the two rear wheels in such manner as to assure their movement in unison during steering. Stem I31 is only engageablerin notch I40 when the rear wheels 2R, 2L are in the straight ahead position, and when so engaged these wheels are locked against steering movement. The ends of the tie rods I28 are connected to the individual wheels by means of arms as I24 rigidly connectedv to and adapted to swing with the steering motor vanesand stub axles of the re: spective wheelsL r r I [Ihe system incorporates'means for preventing turbi e o t e: s e t r.- 'va v v fl awaw om t e 11 e e ered i i nim w i h a ho 4. F g. cept. w ea be m t whe s a ein their str ght ahead positioning. Such means consistsof;- an electromagnetic-loch, the {pre- Iferred embodiment, shown. A hub I08,- is keyed to a squared portion 081 of the stem of-thetvalve rolu ,;-to.-a u t th h la r e ub e nei r vid d a. qu redx a tu eimf nea ble w th th s r d Section of t va e stem, .and-held upon the threaded end 68%.; of the stem by a nut. l03?. I-Iub portion 108 turns. ina (:yliridricai chamber I34 formed in the; rear end ofthe valve casing 61. Aseries of radial-open,- ings I23, ;Ii3 .l23 isformedinthe ,peri-phery ofthe hub-demand a locking plungerfifl, when engaged the opening; I23 holds the ,yalye the centered; Drive? position and againstturne a. Th plu e 9 retr c a o permit the valve to be.- -manually adjusted, undercthe influence of omma-4e acting.upon-anarmature 4:1.to which the plunger 69 is attached; .One terof. the -solenoid.-is. grounda blegby; means of a push button 250-attached to and moyablewvith a rod 252 extending axiallythrough and longitudinally ,slidabie in the valve plug 68' and {its stem portions Ii-8 f, 8 'Ehe rod 252. and;connec t ed parts of the valve structure ,are :fOI'IIlGd'5 of conductive material and; grounded, andyt-he rear end of therod projectabie from the rear. end of the valve. stem to engage-an insulatedcontact 254.;towhich the groundable-terminal :of {the solenoid is connectedasby' the conductor 256. Insulated contact 254 is formed with an integral arm 258 serving in cooperation with insulating washers 280' and-screw 262 to; mount the contact upon w'hile insulating: it from the rearend of the-valve casing 61.- :Theother terminal of the solenoid is i'connected by means of -a conductor I09 ;to a- -wiping contact I 22- engageablezwith .a live contact I18carried by and rotatable with thehub portion -I81 which is formed .ofinsulate ing-material and carried byand; adapted to fturn withan arm. I35 articulated :to the front-wheel tie'rod assembly I21 and so rotatable with and conformable to thesteering;movementof the front wheels: The'contact I181: is' -in effect-the center ;tap'ofa. potentiometer winding I also carried by and rotatable with-insulated hub portion 181. --The wiping contact I11 of. the potentiometeris also engageable with tap I18 when the'wh eels are straight ahead, and contact I11 is. continuously electrically connected to a source of current suchas the storage battery I15 of the vehicle .whenever the ignition switch I80 is closedW 'Ihecontacts-I22, I18 are separatedto break the circuit to the solenoid whenever the front [wheels are turned away from the straight ahead positioning. When these contacts are closed,'ho wever, a'circuit is completed from the battery vto the solenoid 40, as will begapparent, but the; return circuit from the solenoid to ground required to retract. the plunger 69 and permit the selector valve plulg 'fi8rto be turned is onl completed by actuating push button 250 While the wheels are straight ahead. and contacts I22, I18 are engaged. It is thenpossible to'turn valve 63 by means of its handle 68 with which the push button is associated, as shown inFig. 2. The. push button contacts are normally yieldably separated by a spring 253 housed in the valve plug and in itshandle portion; r If when the front wheels are-in. the straightahead position and the .valve 68 is free to -turn i e -..qi e e r e o zpf theplunser .ea

the manne deserib'ed, the telve tstuthe'a "e'e'un:

ter'cl'o'bkwi'se t the position designated Park? and show'n i'n Fig. 4; the hydraulic "circuit is so chariged that the rear wheels are caused to swing with arid in the same directi'cih astlie rrbfht wheels; always remaining parallel thereto; Since all of the wheels may in this fashion be turned to positions 90 with respect to the longitudinal ceriterline of the car, it at/n neteen that the vehicle may be moved sidewis into end But er a parking space, or moved b'odily laterally at any desired angle with respect to the behterliiie, to permit maneuvering in close quarters. With the valve in thisposition, fluid is conducted from the steering valve body-25, during a right turn, through the conduit 93 and valve passage 19 and conduits 94; 91 to the rear wheel stee'ring motor casings BR and H611, enterin these casings upon such sides or the vanes therein as to swing the wheels to the right, as will be apparent. The

fluid discharged from the rear wheel steering motors passe through conduit portions 96, 93 to selector valve port 98, passes through valve passage 16 and then through conduits 99, to the front wheel steering motors, so that the front wheels are simultaneously turned to the right, the fluid from the front wheel motors being returned to the reservoir in the rnahrier previously described. Upon a left turn, with the selector valve in the park position, a; reverse fluid flow occurs to turn all of the wheels t6 the left, the fluid from the steering valve passing first through the front wheel steering motors by Way of fluid Conduits I04; I03, I02, and the discharge from the front steering motors being conducted to the rear steering motors by way of conduits I01, 99, selector valve passage I 8 and conduits 98, 9B. The fluid discharged from the rear wheel steering motors at the same time is returned to the reservoir through conduit 94,

selector valve passage I9, conduit portion 93,

steering valve chamber 34 and return lines 79, 45. With the selector valve turned clockwise from the centered position, to the position designated Turn, and shown in Fig. 5, the fluid circuit is so modified that upon turning of the steering wheel, thefront and rear steerable wheels are swung simultaneously and at corresponding angular rates, but in opposite directions. It

will be seen that this permits turning the ve hicle upon a ver short radius; and even within its own length if desired. With the selector Valve in the Turn' position, the operatibh of ing motors 6R, IIGL, entering the casings of these steering motors at such thereof as :t'o-s'wirig the rear wheels to the left, as will'be apparent; The fluid discharge from the rear wheel steering motors passes through conduits 94, iii-selector valve passage 19 and conduits 93; HJI to the front wheel steering motors l6R; ISL;

entering these motors in a direction to turn ffro'nt wheels to the right, orin the opposite angular direction from the rear Whelsi Upon a left turn of the steering Wheel under tl'i'se conditions, a reverse flow occ'urs' froin the steer ing valve to the front wheelmotors'byway of conduits I04, ms, m, the disc arge from the front steering motors being (jionducted' to the q ie y s r' j. extr tiesp the wheel steering-mete: casings through conduits nit, not, 99; sel'ector valve passage is and condiiits 94,}!; the'di'scharge frbm the rear steering rn'otors being returned to the reservoir as befr A a Bel'easahle loclsing means is also provided for preventing tu'riiingof' the selector valve 68 out or the Parkfl and Turn positions except when the front wheels are straight ahead, and such locking means'may comprise additional sockets I23; [23 functioning similar to socket I23 and erigageable by thep'lunger 69 when the valve is in the Park and Turnf pdsitions respectively and th'e s'ele no'id is not energized.

Ah indicating system is preferably provided and arranged on the instrument panel or in sem ether suitable position within the View of the driver and so arranged as to provide for the driver b'o'th 'a quick indication showing by means of colored lights whether Or-n'ot the front wheels are in the straight-ahead positioning which is necessary to unlock t e selector valve, and an exact representation as to the angular positien occupiedby the wheels at all times. The system also preferably indicates whether or not the rearwheels are locked in the straight-ahead positibnihg which is desirable at all times under ordinary driving conditions; and further provides a vivid indication by means of colored lights wheh the wheels have been swung to the limits 'of their steering movement and are aceo'rdiiigly at ri'g'ht angles to the car.

were a suitable source of current which may cbn ip'ris'e the stdra'ge battery I of the vehicle, the conductor H6 leads to the potentiometer co'ht'act IJ'I previousl mentioned which cooperates with the contacts I22, I18 previously described, The contact H1 is also in wiping engagerneiit with the potentiometer winding I99 as noted above. Opposite extremities of the pote'ritiometerwindirig [90 are connected by means of 'coiiductor s 192, [94 to oppositely acting coils Hi5, [9Q er a dual milliaimm'eter assembly or other suitable electrical measuring device which is preferably of relatively high resistance for the salge of current economy. This meter is generl rds sna b 9 iye be mounte on the instriiment panel of the vehicle in the center of the steering wheel, or in any other convenient rheeth r terminalsof coils we, we rouiidedf as indicated at I98. Coils I95, lfifireact uponan indicating needle 282 which stands in a c 'entered positionwhen both coils ergized or are energized equally. In co'riiiection it will be appreciated thatif des'i ed the twollegs of the winding I90 might, be insul ted from' contact I18 at their inner ends t witlrthe' wheels'wi'n the straight-ahead are turned for ,right steering, the reg 6f. the-potentiometer winding as I, and will in effect be shorth I g the e rrent tothe coil I and sing that to the coil I96 so that the needle r eflected clockwise. The angular fiidtlbn' imparted to the. needle and the calibrations; of the dial ofthemeter may be made to' correspond to degrees of turning movement of the st erab e fv pniiwheels a it i 1'be. .appreciated" that a corresponding reverse movement of 9 the needle occurs upon steering to the left, so that the needle 202 may all times afford an exact indication of the positioning of the front wheels.

A branch conductor 2B4 connected'to the conductor I09 leads to a pilot light 205 which may be colored green'and the other terminal of which is groundedso that it will be illuminated concurrently with energizationof the solenoid 46 to indicate that the front wheels are in their straightahead positioning and that the selector valve is actuatable. When the front wheels are turned about their steering axes to the extreme righthand position, steering motor vane 15L grounds a contact 206 and so completes a circuit through conductor 208 from such contact to a pilot light 2Ill, which may be colored red and so positioned that when illuminated it affords an effective indication that the extreme of right-hand steering movement has been reached. The other terminal of pilot light 2| ll is connected by means of a conductor 212 to the power lead I16. At the limit of full left steering movement of the front wheels. steering motor vane I5R. engages a contact 2I4 housed in appropriate position within steering rintor casing I6R, a circuit being thereby completed by way of conductor 2 I 5 to a pilot light 2I6 which may be colored red and positioned upon the instrument panel in appropriate loca-- tion to indicate that the extreme of left-hand steering movemento-f the front wheels has been reached. The other terminal of pilot light 2; is connected by a conductor 2 I8 to the main power lead I16.

Power lead ,SISis' also extended rearwardly, as indicated at I16, for connection to a potentiometer wiping contact 220 engageable with a potentiometer winding 222 carried by a rear insulated hub portion MI and. corresponding in arrangement and functioning tothe front potentiometer winding I 90 so that the current passing through the two legs of the potentiometer winding is a direct function of their relative length and so of the angular positioning of therear steerable wheels The opposite ends of the potentiometer winding are similarly connected by means of conductors 224, 226 to the actuatin coils 228, 230 of the dual meter construction positioned upon the instrument panel. The inner extremities of the coils 228, 230 may be similarly grounded at I98 and the proportionate energization of these coils-determines the angular positioning of the indicating needle 232 for the rear wheels. It will be apparent that when the rear wheels are turned to the right the increased current in the leg of the potentiometer winding connected to conductor 224 and to coil 228 moves the needle 232 in the corresponding direction, while a reverse actuation and a reverse deflection of the needle occur upon steering of the rear wheels to the left.

I also preferably provide visual indication as to the condition of the rear wheel locking means controlled by the hydraulic cylinder I35, the action of which is described above. When the looking plunger It! is engaged in the socket I 40 to ock the rear wheels in their straight-ahead positioning, it completes a grounding connection to a contact 235 connected by means of a conductor 235 to a pilot light 238 which may be colored green and appropriately positioned upon the instrument panel to indicate that the rear wheels are locked. The other terminal of the pilot light 238 is connected by a conductor 240 and conductor M2 to the main power lead II'i. When the locking plunger I3Iis retracted, it completes tion of the red lamp 245 whenever the rear wheels are unlocked, and the driver is thus warned that the system is not in condition for normal driving.

It will be apparent that various modifications may be introduced without departing from the proper scope and fair meaningof the subjoined claims. I

I claim:

1. A steering system for a vehicle having frontv and rear steerable wheels, said system being adapted to be connected to a source of fluid under pressure, front and rear steering motors adapted to impart steering movements to the front and rear wheels respectively of such a vehicle, flow reversing means interposed between said source and the steering system and responsive to turning movement of a steering wheel or the like for operating said motors in either direction and thereby imparting simultaneous steering movements to the front and rear wheels, means for locking the rear steerable wheels against steering movement without interfering with steering movement of the front wheels, said 1 locking means including a personally operable valve-type control member movable to and from a rear-wheel-locking' position, means normally holding said control member against movement away from rear-wheel-locking position. and means responsive to positioning of the front wheels in straight-ahead-relation for releasing.

said holding means to permit operation of said control member.

2. A steering system for a vehicle having front and rear steerable Wheels, said system being I adapted to be connected to a source of fluid under pressure, front and rear steering motors adapted to impart steering movements to the front and rear wheels respectively of such a vehicle; flow reversing means interposed between said source and the steering system and responsive to turning movement of a steering wheel or the like? for operating said motors in either direction and thereby imparting simultaneous steering -movements to the front and rear wheels, means for locking the rear steerable wheels against steering 1 movement without interfering with steering movement of the front Wheels,said locking means including a personally operable valve-type control member movable to and from a rear-'wjheel-locking position, said valve-type control member including cut-off valve portions for selectively preventing steering movement of the rear steerable wheels when said member is in 'rear-wheel-locking position and also including reversing valve portions to enable imparting steeringmovements to the rear steerablewheels in directions opposite to, but simultaneous with, steering movements imparted to the front steerable wheels, and locking means controllable by the front wheelsfor preventing turning of said control member away from rear-wheel-locking position.

3. Power drive means for a plurality of hydraulic'motors, comprising in combination with a source of hydraulic fluid pressure, means for 11 conducting fluid under pressure to and from each of said motors, a'unitary valving mechanism interposed between at least one of said motors and said source for changing the direction of fluid flow to one of said motors to reverse the relative direction of drive thereof, and means including a mechanical lock and an actuating element there for responsive to the position of another of said motors for locking-said valving means against actuation.

4. Means as set forth in claim '3 in which said valving mechanism incorporates means for interrupting the fluid flowt o said reversible motor to prevent actuation thereof,

5. Power actuating means for a steering system or the like incorporating in combination with a source of hydraulic fluid under pressure, a plurality ofsteerable elements, separate hydraulic driving motors for different ones of said steerable elements, said motors being reversible, means including a selector valve for selectively connecting said motors to said source whereby the motors and the steerable elements may be driven in the same or different directions, means for cutting off the fluid supply to one of the motors, and means including a latch element and a hydraulic actuator therefor for locking an element which is steerable by said last-mentioned motor when the fluid supply to said'motor is cut off.

6. Means as set forth in claim in which said means for cutting ofi the fluid supply is actuatable by and concurrently with said valve, and said hydraulic actuator is also connected to and ac-, tuatable by the valve and in response to movement of the valve to said cutting-off position.

'7. Power steering means for a vehicle having front and rear steerable wheels, comprising in combination with a source of hydraulic fluid under pressure, separate reversible hydraulic motor means for imparting steering movements to'the front wheels and to the rear wheels, a fluid" conveying system for conducting fluid derived from said source to and from'said motor means, means for 'reversing the fluid flow in said system to change-the direction of steering movements'imparted to and by all of the motor means, a unitary selector valve'mechanism also incorporated in said system and including cutoff and reversing lportions connected to the motor means for the rear wheels only, whereby steering movements of the rear wheels may be prevented without interfering with those of the front wheels,

and whereby the relative direction of steering movements imparted to the rear wheels may be reversed with respect to the front wheels, a retractable locking element for mechanically locking the rear wheels against steering movement. and means including a supplemental locking motor device for actuating said locking element 12 means, means for reversing the fluid flow in said system to change the direction of steering movements imparted to and by all of the motor means, a unitary selector valve mechanism also incorporated in said system and including cutofi and reversing portions connected to the motor means for the rear wheels only, whereby steering movements of the rear wheels may be preve'nted without interfering with those of the front wheels, and whereby the relative direction of steering movements imparted to the rear wheels may be reversed with respect to the front wheels, means responsive to movement of the front wheels out of a predetermined position for restraining operative movement of said selector valve.

9. Power drive means for a plurality of hydraulic motors, comprising in combination with a source of hydraulic fluid pressure, means for conducting fluid under pressure to and from each latch actuating means, and steerable members actuat'ablelby said motors, said disabling means being actuatable in response to movement of at least one of said steerable members away from a predetermined position.

10. In a remotely controllable power-actuated steering system for vehicles and the like, in

combination with a steerable element and motor means for imparting steering-movement thereto, and with control means located at a control station remote from the motor means and from the steerable element for controlling the action of such motor means and steerable element, indicating means located at such control station includinga meter having a member movable conformably to steering movements of the steerable element, and means located appurtenant the steerable element and arranged in an electrical circuit with said meter, said means appurtenant the steerable element including a member movable to change a parameter of said circuit which includes said meter, to actuate the meter in'response to steering movements of the steerable element,

BLONDA O. STROTHER.

' REFERENCES CITED ,The following references are of record in th file of this patent:

UNITED STATES PATENTS in response to' positioning of said selector valve mechanism in such position" as to cut off fluid Number Name I Date flow to the rear wheel motor means. 86 ,2 Macfarren oict- 1997 8. Power steering means for a vehicle having 1,928,915 Stout Oct. 3, 1933 front and rear steerable wheels, comprising in 54,296 Merrill Sept. 15, 1936 combination with a source of hydraulic fluid 2,178,073 Hardy Oct. 31, 1939 under pressure, separate reversible hydraulic 2,184,793 Clench Dec. 26, 1939 motor means for imparting steering movements 2,206,163 Clench July 2, 1940 to the front wheels and to the rear wheels, a 2,248,251 Reeves July 8, 1941 fluid conveying system for conducting fluid de- 2.336.715 Casler Dec, 14, 1943 rived from said source to and from said motor 

